One serious drawback to many plastics used in the manufacture of fluid containers is that they are gas and liquid permeable so that the gas and/or liquid contents can escape through the container wall. Different plastics have different permeability rates, but those presently being used in the manufacture of containers for liquids such as carbonated beverages and the like all share this problem.
One approach to the problem has been to coat plastic containers with a "barrier" material such as polyvinylidene chloride (PVDC). However, if the coating is applied on the outside of the container, the fluid contents can still penetrate the container wall and will often produce blisters in the coating. As a result, the container takes on an unsightly appearance, and, of course, there is a loss of some of the fluid contents (CO.sub.2 in the case of carbonated beverages). Outside coating by the "dip method" has also been found to be expensive in terms of time and labor, and to result in an uneven distribution of coating.
On the other hand, inside coating, while it avoids blistering resulting from internal fluid pressure, is a difficult and costly procedure requiring increased drying time. Moreover, any flaking of the coating will contaminate the contents.
In accordance with the specific embodiment described hereinafter, a label or the like is applied to a plastic container by a process known as In-Mold Labeling. The label is resistant to fluid transmission and has a heat-sensitive adhesive surface. The label is placed in the mold; then plastic heated to a temperature sufficient to activate the adhesive is introduced into the mold and forced against the wall of the mold and against the label to form the container and to cause the label to adhere to the container thus formed. The label for all practical purposes becomes an integral part of the container so that it will not blister or peel away, and resists fluid transmission through the label area. The label area usually has a relatively thin wall compared to other parts of the container and thus the portion of the container having the least resistance to gas and liquid transmission is protected.
These and other objects and features of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings.